1. Field of the Invention
This invention relates generally to an imaging system for photographically recording electronic signal information and, more particularly, to an imaging system for recording on a photosensitive medium an image defined by electronic signal information in binary word format.
2. Description of the Prior Art
Light emitting diode arrays are well known in the art for recording an image on a photosensitive medium such as a film or paper or, alternatively, a photocopying receptor such as a selenium drum or a zinc oxide paper. In order to achieve high resolution, a large number of light emitting diodes are arranged in a linear array and means are included for providing a relative movement between the linear array and the photosensitive medium so as to affect a scanning movement of the linear array over the surface of the photosensitive medium. Thus, the photosensitive medium may be exposed to provide a desired image one line at a time as the LED array is advanced relative to the photosensitive medium either continuously or in a stepping motion. Each LED in the linear array is used to expose a corresponding pixel in the photosensitive medium to a value determined by image defining electronic signal information. In one conventional approach, the LED's are driven by a constant current and the exposure value is determined by controlling the time during which the LED is driven to an on condition. Thus, in this approach the LED is time modulated while the current and hence the light output from the LED are maintained at a substantially constant value.
The aforementioned time modulation technique may be implemented using a linear LED array by sequentially driving each LED on for a time interval proportional to the desired exposure value. The LED's may be sequentially driven in a well-known manner by a timer primed with the image defining electronic signal information in binary format so as to control the duration of the interval at which each LED is driven on via a fixed frequency clock. This sequential exposure scheme, however, requires too long a time to expose an entire image frame to be practical for many applications.
Therefore, it is a primary object of this invention to provide an apparatus and method utilizing an LED array for recording on a photosensitive medium an image defined by electronic signal information in a substantially shorter time period than is heretofore been accomplished.
It is a further object of this invention to provide an apparatus and method for recording with an LED linear array on a photosensitive medium an image defined by electronic signal information in binary word format by simultaneously controlling the energization of all the LED's in selected different time intervals so as to substantially shorten the overall exposure time required.
Other objects of the invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises a mechanism and system possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.